engleski

Structures of Two Novel penam Derivatives

The X-ray structure analysis of both optically active penam derivatives (2S, 4S, 5R, 6S)-2-benzylcarbamoyl-6-bromo-3, 3-dimethyl-7-oxo-4-thia-1- azabicyclo[3.2.0]heptane-4-oxide, C~15~H~17~BrN~2~O~3~S.H~2~O (I), and (5R)-3-benzylimino-2-isopropylidene-7-oxo-4-thia-1-azabicyclo[3.2.0]heptane, C~15~H~16~N~2~OS (II), have been determined in order to ascertain their absolute configuration. Both compounds adopted open-book conformation of fused beta-lactam and thiazolidine ring. The beta-lactam ring is in a distorted planar conformation while the thiazolidine ring is in an envelope conformation. Pyramidalisation effect of the N1 atom in both compounds has been characterised by nitrogen shift from the plane of its substituents of 0.344(5) and 0.350(5) %A in molecules A and B in compound (I), as well as of 0.410(5) %A in compound (II).

penam ; optically active ; x-ray crystallography ; conformation

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